Isomerization of 2-phenyl alkanes



United States Patent 3,352,933 ISOMERIZATION 0F Z-PHENYL ALKANES Harold A. Sorgenti, Philadelphia, Pa, assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Filed Dec. 7, 1965, Ser. No. 512,197

3 Claims. (Cl. 260668) This invention relates to an isomerization process. In a further aspect, the invention relates to an improvement in the production of biodegradable detergents.

Straight chain alkylbenzenes having 9 to 15 carbon atoms in the alkyl chain are necessary intermediates in the preparation of C -C straight chain alkylbenzene sulfonates which are well known and widely used biodegradable detergents. It is known that these alkylbenzene sulfonates have better over-all surface active properties when the phenyl group is not bonded to a 2 carbon atom of the alkyl group, a carbon atom adjacent to the terminal carbon atom. Unfortunately it is not possible utilizing commercial methods for preparing the intermediate alkylbenzenes to prevent the formation of alkylbenzenes having the benzene ring bonded to the number 2 carbon atom of the alkyl side chain. More specifically, when benzene is alkylated with a C9-C15 normal olefin or mixtures thereof or with a C -C normal alkyl chloride or mixtures thereof in the presence of aluminum chloride alkylation catalyst, all of the possible isomers of the resulting alkylbenzenes are produced. Thus, there will be obtained a very small percentage of alkylbenzenes wherein the benzene ring is bonded to the terminal carbon atom of the alkyl side chain and greater percentages of alkylbenzene wherein the benzene ring is bonded to the second, third, fourth, etc. carbon atom of the alkyl chain. Under the alkylation conditions normally employed there may be produced anywhere from to 34 weight percent of the 2-phenyl isomer. If this mixture of alkylbenzene isomers is sulfonated and neutralized to prepare the detergent product there is obtained a detergent that has poorer surface active properties than if there were smaller amounts or no 2- phenyl isomer present.

In the alkylation, the 2-phenyl isomer equilibrium amount is in the range of 30-34 weight percent depending upon process variables and average carbon number of the alkylate. It has been the custom to separate the 2- phenyl isomer and to use the other isomers for the production of heavy duty detergent. Following this separation, there has been no economical and convenient means for isomerizing the Z-phenyl isomer to one of the more desirable isomers.

The following are objects of my invention.

An object of my invention is to provide an improved process for isomerizing a hydrocarbon mixture containing a substantial amount of 2-phenyl alkanes. A further object of the invention is to provide an improved process for the production of detergent alkylates in which it is not necessary to prepare the sulfonate from a stream containing a substantial amount of the 2-phenyl isomer.

Other objects and advantages of my invention will be apparent to one skilled in the art upon reading this disclosure.

Broadly, my invention resides in a process for the treatment of a Z-phenyl alkane stream boiling in the detergent alkylate range containing at least 85 weight percent alkylbenzenes to produce a stream containing reduced 2-phenyl alkane content without substantially decreasing the monoalkylbenzene content of the total alkylate which comprises adding to said 2-phenyl alkane stream benzene to provide a volume ratio of benzene to 2-phenyl alkane of 1:1 to 10:1, adding to said Z-phenyl alkane stream a parafi'in hydrocarbon having approximately the same number of carbon atoms as the alkyl group in said phenyl alkane to provide a volume ratio of paraflin to 2-phenyl alkane of 1:1 to 10:1, adding aluminum chloride catalyst of such concentration and of such activity to provide a catalyst severity of at least 0.10 when the subsequent reaction is carried out at F. and at least 0.05 When the subsequent reaction is carried out at 220 F., said severity decreasing linearly as the temperature increases in said range of 135 F. to 220 F., and reacting the resulting mixture at a temperature in the range of 135 to 220 F. until a substantial amount of the 2-phenyl alkane has been isomerized to other isomers. Furthermore, the upper limit of catalyst severity decreases as the temperature increases. Generally, the maximum severity is 0.25 at 135 F. and it decreases linearly to 0.15 at 220 F.

From this description, it will be apparent that a number of features are necessary for carrying out my invention. One of the important differences is the catalyst severity used. The catalyst severity for my process is considerably higher than that used in normal alkylation work. Catalyst severity is determined by multiplying the concentration of the aluminum chloride by the catalyst activity factor.

Catalyst activity as used herein may be calculated from the following formula:

1 D A 'htClS- wherein X is the fraction of l-chlorododecane converted to dodecylbenzene under reaction conditions described hereinafter; C is the aluminum chloride concentration in moles per liter; C is the benzene concentration in moles per liter; t is the reaction time in minutes; I is the catalyst activity factor; k is the reaction rate con stant for primary chloride (a function of temperature); and where the value of k at three representative temperatures is 200 at 250 F., 32 at 200 F., and 12 at F., the units of k being (moles/liter) (rninutes) Since the plot of the ln k versus 1/ T, where T is the absolute temperature, is a straight line, the value of k at any temperature may be found from the representative values set forth above.

To determine the catalyst activity 1 milliliter of the liquid aluminum chloride catalyst complex is added to a mixture of 16.7 milliliters of benzene, 3.3 milliliters of l-chlorododecane, and 30.0 milliliters of dodecane which has been dried over magnesium sulfate. The mixture is heated to a temperature of 200 F. One minute after the addition of the liquid aluminum chloride catalyst complex to the reaction mixture a sample of the reaction mixture is taken and analyzed by *gas chromatography to determine the quantity of l-chlorododecane which has been converted, i.e. X The activity of the catalyst k can then be calculated as k is 32, z is 1 minute, and C and C are also known. This determination is further discussed in application Ser. No. 433,327, filed Feb. 17, 1965, of which I am a co-inventor. Rather than make the calculations, k may be determined from FIG- URE 1 of said copending application wherein by measuring the fraction of 1-chlorododecane that has been converted the catalyst activity may be directly read.

Calculations of the amount of the alumintun chloride slurry can probably best be understood by considering a sample calculation. Before the 2-phenyl alkane isomerization is run, a catalyst slurry would be obtained from previous alkylation. Such a slurry would then be satmated with fresh aluminum chloride as is ordinarily practiced in the industry and the aluminum chloride content determined by standard analytical procedure. It would then be necessary to run the test to determine the catalyst activity, the term k in the equation. This would be done "by alkylating benzene with the chloroparafiin according to the method outlined above. If we assume a 90% conversion in one minute, the catalyst activity can be determined from the equation or from FIGURE 1 of said application Ser. No. 433,327. According to FIG- URE 1, the conversion of 90% corresponds to a catalyst activity of 0.6. The next step is to determine the severity desired for a particular reaction and for these initial calculations, it can be assumed as 0.05, one of the limits for the carrying out of my invention. Since catalyst severity is equal to the product of the activity times the concentration (C this severity would require 0.083 gram mole of aluminum chloride per liter of reaction mixture, this being the figure obtained when the severity, 0.05, is divided by the activity, 0.6. Then, further assuming .a reaction vessel capable of handling approximately 1500 liters per hour, the reaction would be carried out by feeding 100 liters per hour of the alkylate, 500 liters per hour of benzene and 900 liters per hour of the paraflin. The product of the number of liters per hour times the gram moles of aluminum chloride per liter gives 127.5 gram moles of aluminum chloride needed per hour. Specifically, the 127.5 is obtained by multiplying 1537 total liters charged by 0.083. Dividing the 127.5 gram moles of aluminum chloride needed per hour by the moles of aluminum chloride per 100 grams of slurry as determined in the standard analytical procedure where 0.3 may be considered typical gives the required number. of grams of slurry neded per hour; 42,500 grams in this case. To convert to volume, this figure as divided by the slurry density (where 1.15 grams per cc. is typical) will give the number of cubic centimeters of slurry per hour. Conversion to liters, gives 36.9 liters per hour in this case.

The dilution of the feed stream is important and is the result'of the addition of two additional components to the high 2-phenyl alkane stream. One of the added materials is benzene, and, as stated, this should be used in an amount to provide a volume ratio of benzeneto 2- phenyl alkane of 1:1 to 10:1. The added benzene reduces the production of light ends and polyalkylated products and makes the process otherwise: operable. Also, there should be added a parafiinic hydrocarbon to provide. a volume ratio of paraffin to Z-phenyl alkane of 1:1 to 10:1. The parafiin is believed to serve as a source of hydrogen, this preventing undesirable side reactions resulting in the formation of undesiredheavy alkylate and light ends. For best results, the paraffinic hydrocarbon contains paraffins containing the same number of carbon atoms present in the alkyl chain in the phenyl .alkane. This is not critical and mixtures of hydrocarbons can be used as long as they have approximately the same number of carbon atoms as the alkyl groups.

Another distinguishing feature of the invention resides in the isomerization tern peratures used. The range of l35220 F. is considerably above that normally used for aluminum chloride alkylation and isomerization work. Within this number range, I prefer to operate in the temperature range of 175210 F. and, so far as I know, no one has carried out isomerization on a commercial scale at such high temperatures.

In my invention one can use hydrogen chloride or other hydrogen halide during the isomerization reaction. The addition of small amounts of the hydrogen halide provides somewhat greater catalyst activity. Specifically, at the same catalyst severity levels, the addition of hydrogen chloride results in a lower 2-phenyl content in thetotal alkylbenzene produced, other conditions being the same. In the same manner, a lower catalyst severity level can be used to obtain the same 2-phenyl content if the hydrogen halide is present.

The use of my process does .not substantially change the usual detergent production process. However, certain additional steps are, obviously, necessary. In one process, benzene is alkylated with alkyl chlorides in the presence of aluminum chloride catalyst. As is well known, the aluminum chloride reacts with hydrocarbons present in the system to produce a catalytically active sludge. So far as this sludge is concerned, my process does not vary from those of the priorart. Following the production of the alkylate, the resulting stream is fractionated to produce a parafiin recycle stream which is generally returned to the chlorination reactor, and an alkylated product. The alkylate stream is then fractionated, taking advantage of the difference in boiling points between the undesirable 2- phenyl isomer and the other alkylbenzenes present to produce a low 2-phenyl heart out alkylate overhead product and a high Z-phenyl-heavy alkylate mixture as a bottoms product. The 2-pheny1 isomer stream is then flashed or otherwise treated to produce a stream containing substantially pure above weight percent) 2-phenyl isomer. This separation step iscarried out because, as shown hereinafter, the heavier products interfere with the isomerization. The 2-phenyl isomer. stream is then isomerized following the addition of the paraffin, the benzene, and the catalyst. In the isomerizatioman equilibrium mixture of the various isomer is again produced or (at least approached) this producing a stream which is fractionated to give a stream containing a majority of the desired isomers which can then be sent to sulfonation and the Z-phenyl alkane stream which is recycled to the isomerization reactor.

The following examples illustrate specific embodiments of my inventionbut they should not be considered unuly limiting.

Example 1 A high 2-phenyl alkane feedstock was prepared by fractionating a previously prepared alkylate. This feedstock had the following composition:

Weight percent Monoalkylbenzenes 95.4 Indanes (C H 2.6 Diphenyls (C H 0.3 other n 2n-10, -12, etc.) This stream contained 77 weight percent Z-phenyl alkanes. Thus, 81 weight percent of the phenyl alkanes Was the 2 isomer. In each of these runs 5 volumes of henzene were added per volume of alkylate. Details of the runs are shown in the following table.

TOTAL ALKYLATE COMPOSITION-WT. PERCENT Alkybenzenes Run No. P fin era 2-Ph Temp, Catalyst Time, added, On and Heart Disubsti- Indanes Diphenyls Others reiiiiiii if? F. Severity min. vol./vol. tr. Cut tuted (CHEM-s) (CnH2n-14) (CnH2n-10, 12 Heart Out alkylate etc.) Monoalkyl- Benzeues 7 Charge 95. 4 2. 6 0.3 1. 1 0. 080 30 9/1. 95. 4 3- 3 0.1 1. g 135 0. 040. 30 9/1 O) 0) 79-7 135 0. 154 60 9/1 0. 04 93. 6 1. 5 3. 1 O. 8 0. 96 44 135 0.183 60 None 91. 5 2. 8 3. 7 1. 3 0. 7 36 200 0.080 60 9/1 0.1 91. 1. 0 3. 0 0. 8 4. 0 40 200 0. 154 60 9/1 0. 7 77. 2 1. 6 14. 5 l. 8 4.2 32

1 Not completely analyzed, no reaction.

This table illustrates some of the important features of my invention. The Heart Cut is the weight percent alkylbenzenes with the same number of carbon atoms as the charge. In the first place, one can see that there is a definite relationship between temperature and catalyst severity, lower severity being required with increased temperature. At the 0.080 severity level the isomerization was proceeding very slowly at 135 F. but a satisfactory rate was obtained at 200 F. Run 4 shows that the formation of heavy alkylate (dialkylbenzenes) is substantially increased when the paraffin is not used. Further, a comparison of Runs 5 and 6 shows controlling catalyst severity is critical since at the higher severity a significant loss of heart out monoalkylbenzenes occurs.

Example 2 When the feed to the isomerization contains heavy ends such heavy ends interfere with the isomerization as shown by this example wherein a feed of the following composition was used.

This stream had a boiling range of 597 F. to higher than 650 F. The Z-phenyl alkane content was 78 weight percent of the monoalkylbenzenes present. An attempt was made to isomerize this feed using 5 volumes of added benzene, 9 volumes of parafiin and an AlCl catalyst severity of 0.154. With a reaction time of 60 minutes the product had a 2-phenyl alkane content of 61 weight percent of the monoalkylbenzenes present, this being far lower than the runs of the invention in Example 1.

As many possible embodiments can be made of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth is to be interpreted as illustrative and not as unduly limiting the invention.

I claim:

1. A process for the treatment of a Z-phenyl alkane stream boiling in the detergent alkylate range containing at least weight percent monoalkylbenzenes to produce a stream containing reduced 2-phenyl alkane content without substantially decreasing the monoalkylbenzene content of the total alkylate which comprises adding to said Z-phenyl alkane stream benzene to provide a volume ratio of benzene to 2-phenyl alkane of 1:1 to 10:1, adding to said 2-phenyl alkane stream a parafiin hydrocarbon having approximately the same number of carbon atoms as the alkyl group in said phenyl alkane to provide a volume ratio of paraflin to 2-phenyl alkane of 1:1 to 10:1, adding aluminum chloride catalyst of such concentration and of such activity to provide a catalyst severity of at least 0.10 when the subsequent reaction is carried out at F. and at least 0.05 when the subsequent reaction is carried out at 220 F., said severity decreasing linearly as the temperature increases in said range of 135 F. to 220 F., and reacting the resulting mixture at a temperature in the range of 135 F. to 220 F. until a substantial amount of the 2-phenyl alkane has been isomerized to other isomers.

2. The process of claim 1 wherein the temperature is between and 210 F.

3. The process of claim 1 wherein the maximum severity of 0.25 at 135 F. and 0.15 at 220 F., said severity decreasing linearly as the temperature increases in said range of 135 F. to 220 F.

References Cited UNITED STATES PATENTS 5/ 1967 Rubinfeld.

OTHER REFERENCES PAUL M. COUGHLAN, JR., Primary Examiner. C. R. DAVIS, Assistant Examiner. 

1. A PROCESS FOR THE TREATMENT OF A 2-PHENYL ALKANE STREAM BOILING IN THE DETERGENT ALKYLATE RANGE CONTAINING AT LEAST 85 WEIGHT PERCENT MONOALKYLBENZENES TO PRODUCE A STREAM CONTAINING REDUCED 2-PHENYL ALKANE CONTENT WITHOUT SUBSTANTIALLY DECREASING THE MONOALKYLBENZENE CONTENT OF THE TOTAL ALKYLATE WHICH COMPRISES ADDING TO SAID 2-PHENYL ALKANE STREAM BENZENE TO PROVIDE A VOLUME RATIO OF BENZENE TO 2-PHENYL ALKANE OF 1:1 TO 10:1, ADDING TO SAID 2-PHENYL ALKANE STREAM A PARAFFIN HYDROCARBON HAVING APPROXIMATELY THE SAME NUMBER OF CARBON ATOMS AS THE ALKYL GROUP IN SAID PHENYL ALKANE TO PROVIDE A VOLUME RATIO OF PARAFFIN TO 2-PHENYL ALKANE OF 1:1 TO 10:1, ADDING ALUMINUM CHLORIDE CATALYST OF SUCH CONCENTRATION AND OF SUCH ACTIVITY TO PROVIDE A CATALYST SEVERITY OF AT LEAST 0.10 WHEN THE SUBSEQUENT REACTION IS CARRIED OUT AT 135*F. AND AT LEAST 0.05 WHEN THE SUBSEQUENT REACTION IS CARRIED OUT AT 220*F., SAID SEVERITY DECREASING LINEARLY AS THE TEMPERATURE INCREASES IN SAID RANGE OF 135*F. TO 220*F., AND REACTING THE RESULTING MIXTURE AT A TEMPERATURE IN THE RANGE OF 135*F. TO 220*F. UNTIL A SUBSTANTIAL AMOUNT OF THE 2-PHENYL ALKANE HAS BEEN ISOMERIZED TO OTHER ISOMERS. 